We report on the production of a stable mixture of bosonic and fermionic superfluids composed of the elements ${}^{174}\mathrm{Yb}$ and ${}^6\mathrm{Li}$ which feature a strong mismatch in mass and distinct electronic properties. We demonstrate elastic coupling between the superfluids by observing the shift in dipole oscillation frequency of the bosonic component due to the presence of the fermions. The measured magnitude of the shift is consistent with a mean-field model and its direction determines the previously unknown sign of the interspecies scattering length to be positive. We also observe the exchange of angular momentum between the superfluids from the excitation of a scissors mode in the bosonic component through interspecies interactions. We explain this observation using an analytical model based on superfluid hydrodynamics.

We report on a general method for the rapid production of quantum degenerate gases. Using ${}^{174}\mathrm{Yb}$, we achieve an experimental cycle time as low as 1.6–1.8 s for the production of Bose-Einstein condensates (BECs) of $(0.5–1)\times {10}^5$ atoms. While laser cooling to $30\mu \mathrm{K}$ proceeds in a standard way, evaporative cooling is highly optimized by performing it in an optical trap that is dynamically shaped by utilizing the time-averaged potential of a single laser beam moving rapidly in one dimension. We also produce large $\left(>{10}^6\right)$ atom number BECs and successfully model the evaporation dynamics over more than three orders of magnitude in phase space density. Our method provides a simple and general approach to solving the problem of long production times of quantum degenerate gases.

We report on the realization of an ultracold mixture of lithium atoms in the ground state and ytterbium atoms in an excited metastable (${}^3{P}_2$) state. Such a mixture can support broad magnetic Feshbach resonances which may be utilized for the production of ultracold molecules with an electronic spin degree of freedom, as well as novel Efimov trimers. We investigate the interaction properties of the mixture in the presence of an external magnetic field and find an upper limit for the background interspecies two-body inelastic decay coefficient of $K_2^{\prime }<3\times {10}^{-12}{\mathrm{cm}}^3/\mathrm{s}$ for the ${}^3{P}_2$ $m_J=-1$ substate. We calculate the dynamic polarizabilities of the $\mathrm{Yb}({}^3{P}_2)$ magnetic substates for a range of wavelengths, and find good agreement with our measurements at 1064 nm. Our calculations also allow the identification of magic frequencies where Yb ground and metastable states are identically trapped and the determination of the interspecies van der Waals coefficients.

Quantum-degenerate mixtures of one-electron and two-electron atoms form the starting point for studying few- and many-body physics of mass-imbalanced pairs as well as the production of paramagnetic polar molecules. We recently reported the achievement of dual-species quantum degeneracy of a mixture of lithium and ytterbium atoms. Here we present details of the key experimental steps for the all-optical preparation of these mixtures. Further, we demonstrate the use of the magnetic field gradient tool to compensate for the differential gravitational sag of the two species and control their spatial overlap.

VIPR (vapor in-cloud profiling radar) is a tunable G-band radar designed for humidity and cloud remote sensing. VIPR uses all-solid-state components and operates in a frequency-modulated continuous-wave (FMCW) radar mode, offering a transmit power of 200–300 mW. Its typical chirp bandwidth of 10 MHz over a center-frequency tuning span of 167–174.8 GHz results in a nominal range resolution of 15 m. The radar’s measured noise figure over the transmit band is between 7.4 and 10.4 dB, depending on its frequency and hardware configuration, and its calculated antenna gain is 58 dB. These parameters mean that with typical 1 ms chirp times, single-pulse cloud reflectivities as low as −26 dBZ are detectable with unity signal-to-noise at 5 km. Experimentally, radar returns from ice clouds above 10 km in height have been observed from the ground. VIPR’s absolute sensitivity was validated using a spherical metal target in the radar antenna’s far-field, and a G-band switch has been implemented in an RF calibration loop for periodic recalibration. The radar achieves high sensitivity with thermal noise limited detection both by virtue of its low-noise RF architecture and by using a quasioptical duplexing method that preserves ultrahigh transmit/receive isolation despite operation in an FMCW mode with a single primary antenna shared by the transmitter and receiver.

Differential absorption radar (DAR) offers an active remote sensing solution to the problem of measuring humidity profiles with high vertical and horizontal resolution in hydrometeor layers. The Vapor In-Cloud Profiling Radar (VIPR) is a frequency-modulated continuous-wave (FMCW) G-band DAR tunable from 167 to 174.8 GHz being developed at the Jet Propulsion Laboratory (JPL). Here we describe ground-based measurements from VIPR performed at the Department of Energy’s Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) site for humidity product validation. Two distinct measurement capabilities are investigated: 1) humidity profiles inside of cloudy volumes with 180 m vertical resolution, and 2) integrated water vapor (IWV) between the surface and cloud base. High radar sensitivity permits detection of upper-tropospheric clouds and retrieval of humidity profiles above 10 km in height. We develop an improved humidity retrieval algorithm based on a regularized least squares method that includes detailed accounting of measurement covariances and systematic error sources. This regularization mitigates high-spatial-frequency humidity biases that arise from frequency-dependent hydrometeor scattering, which is an important limitation for DAR systems. Through comparisons with over 20 coincident radiosondes, we find close agreement between in situ and remotely sensed humidity profiles, with a correlation coefficient of r = 0.96, root-mean-square error (RMSE) of 0.8 g m⁻³, and median retrieval precision of 0.5 g m⁻³. Using a merged radiosonde and Raman lidar product for surface-to-cloud-base IWV, we demonstrate precise column sounding capabilities with r = 1.00, RMSE of 1.2 mm, and median retrieval precision of 0.25 mm.